The present invention is directed to a cutting tool for forming undercuts or circumferentially extending widened sections in boreholes in a hard material component such as masonry, concrete and similar materials. The cutting tool includes a drive shaft and a cutting member at the leading end of the drive shaft. The cutting member has an axially extending shank section with a head containing cutting elements at an end of the shank section projecting from the drive shaft.
The German Offenlegungsschrift DE-OS 24 15 240 discloses a tool for forming cylindrical boreholes with a radial widening of the borehole as the tool advances. The tool includes a rotatable drive shaft, with a cutting head pivotably supported at the leading end of the shaft. A cardan joint provides the pivotable support for the cutting head.
To form the undercuts, the cutting head must be displaced by the drive shaft in a drilling direction with simultaneous rotation, whereby the cutting head pivots outwardly relative to the axis of the drive shaft. The rotary motion of the drive shaft is transmitted by the cardan joint to the cutting head. Such rotary motion of the cutting head around its own axis can lead to jamming, for instance when it impacts gravel or reinforcing steel causing malfunctions and high wear. Additionally, the undercuts can be located at different depths because of the type of undercut formation by displacement of the drive shaft in the borehole and different shapes of the borehole may be formed, which can lead to disadvantages when setting expansion anchors into such boreholes.